A man shot and wounded his sister, fatally shot his nephew then turned the gun on himself Monday night in their Valinda home, a detective said.

Another nephew fled the home and called 911.

Paramedics took the 60-year-old woman and her 18-year-old son to a local hospital area where the teenager later died, according to Sheriff’s Homicide Lt. John Corina. The woman was last listed in critical condition.

Corina identified the victims as Jeanita Griego and her son, Ezekiel Griego.

The shooter, identified by Corina as 64-year-old Thomas Stratton, died at the scene. Deputies recovered a handgun at the house.

Tuesday morning, authorities were still outside the home in the 1800 block of Gretta Avenue. The coroner removed Stratton’s body around 7:40 a.m.

According to sheriff’s investigators, there appeared to be an ongoing dispute between brother and sister that may have been related to their living arrangement.

“Looks like (it was) building up over time. He was upset,” Corina said.

Corina said the sister wanted Stratton out of the house. He said deputies were called to the house about a month ago on a disturbance but didn’t know the details.

Stratton had been recently arguing with his sister.

Jeanita Griego and her 18-year-old son were sitting in the back patio area Monday night when Stratton shot them in the heads, Corina said. Griego’s older son heard the shooting and the saw the aftermath.

“He saw the uncle with the gun and got out of the house,” Corina said.

Stratton went back to his room and shot himself in the head, according to the lieutenant.

Oscar Leyva lives on the block but didn’t hear gunshots. The barking of the neighbor’s dogs drew him outside. Leyva saw one of the neighbor’s sons run from the backyard to the front yard. He said the young man was screaming that his uncle shot his mother and brother.

“He said the uncle is drunk or under the influence,” Leyva said. “I told him, ‘Come here. Come here.”

When the young man asked if he had a phone, Leyva called 911 shortly before 7:30 p.m. then handed the phone over to the man.

The man told dispatchers that he ran out of the house in fear that his uncle was going to shoot him next, according to a sheriff’s statement.

Connie Sanchez of Santa Clara was visiting her cousin who lives next door to the suspect. Sanchez and others just came back from dinner and were sitting down when they heard two loud pops. She said it happened between 7 and 7:10 p.m,

Sanchez saw a young man running through the side yard of the neighbor’s house. He was grabbing his head and screaming.

“He said, ‘He shot my mom and my little brother!,’” Sanchez said, adding that the young man went across the street and sat on a neighbor’s yard. She said he was in distress.

She asked him if his mother and brother were OK and told him they needed to call 911.

“He said, ‘No. They’re dead. They’re dead,’” Sanchez said.

Sanchez’s cousin, Maria Baltodano, was not home when the shooting occurred. When she arrived home, Baltodano said deputies were already in the neighborhood.

“First we thought he (the suspect) had left because they came with guns. But he was there,” Baltodano said.

Authorities ask anyone with information about the shooting to call the Los Angeles County Sheriff’s Department’s Homicide Bureau at 323-890-5500. Tipsters can provide information anonymously by calling Crime Stoppers at 800-222-TIPS (8477), by using the P3 Tips mobile app or by using the website lacrimestoppers.org.